CN112048060A - Side chain type liquid crystal ionomer containing benzoxazole liquid crystal elements and preparation method thereof - Google Patents
Side chain type liquid crystal ionomer containing benzoxazole liquid crystal elements and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of materials, and discloses a side chain type liquid crystal ionomer containing benzoxazole liquid crystal elements and a preparation method thereof. The structural formula of the liquid crystal ionomer is
Description
Technical Field
The invention belongs to the technical field of materials, and relates to a liquid crystal ionomer and a preparation method thereof, in particular to a side chain type liquid crystal ionomer containing benzoxazole liquid crystal elements and a preparation method thereof.
Background
The liquid crystal ionomer is developed on the basis of a liquid crystal polymer and an ionic polymer, comprises a main chain type liquid crystal ionomer, a side chain type liquid crystal ionomer and the like, has the ordering of the liquid crystal polymer and the ionic conductivity of the ionic polymer, and is widely applied to the aspects of polymer additives, high-strength fibers, coatings, membrane materials and the like.
The difficulty in synthesizing the liquid crystal ionomer structure is high, and the introduction of liquid crystal elements and the construction of ionic groups are ensured. Although the existing main chain type liquid crystal ionomer can obtain stable liquid crystal phase behavior, the copolymerization degree is difficult, and the ionomer with high molecular weight is difficult to obtain; the prior side chain type liquid crystal ionomer takes the liquid crystal element mainly comprising cholesteryl and aromatic ester structures, such as prepared by Zhang Bao research topic group
And side chain cholesteric liquid crystals
In the structure of these liquid crystal ionomers, mesogens are introduced into the polymer backbone structure as side chains after being linked by ester groups. However, the chemical structure of the ester group is easy to hydrolyze and break bonds under certain humidity and acid/alkali conditions, and the problem seriously influences the stability of the side chain type liquid crystal ionomer based on the ester group linkage and the application development thereof.
Therefore, the synthesis of the side chain type liquid crystal ionomer which has relatively simple and efficient preparation process, particularly has no easily hydrolyzed ester group-linked liquid crystal unit, good structural stability and good liquid crystal performance has extremely important significance in the technical field of liquid crystal materials.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a side chain type liquid crystal ionomer containing benzoxazole liquid crystal elements, wherein a liquid crystal monomer is connected with a main chain through nucleophilic substitution reaction, the defect that the traditional ester bond connection is easy to hydrolyze is avoided, the stability is good under certain humidity and acid/alkali environment, the liquid crystal ionomer is not easy to hydrolyze, and meanwhile, the liquid crystal ionomer has a two-dimensional ordered smectic phase focal conic texture and is beneficial to chloride ion conduction;
the invention also aims to provide a preparation method of the side chain type liquid crystal ionomer containing benzoxazole liquid crystal elements.
In order to achieve the purpose, the invention adopts the following technical scheme:
a side chain type liquid crystal ionomer containing benzoxazole liquid crystal elements has a structural formula as follows:
wherein x/y is more than or equal to 0.2/1 and less than or equal to 1.2/1.
The invention also provides a preparation method of the side chain type liquid crystal ionomer containing benzoxazole liquid crystal elements, which comprises the following steps:
s1: preparation of benzoxazole mesogen
Reacting p-hydroxybenzaldehyde, 1, 6-dibromohexane, anhydrous potassium carbonate and N, N-dimethylformamide, and separating and purifying to obtain an intermediate product A;
reacting the intermediate product A, 2-amino-4-chlorophenol and dichloromethane, and recrystallizing to obtain an intermediate product B;
reacting the intermediate product B with dichlorodicyano benzoquinone, separating, purifying and recrystallizing to obtain an intermediate product C;
reacting the intermediate product C and thiourea with absolute ethyl alcohol and sodium hydroxide to obtain benzoxazole liquid crystal cells, wherein the structural formula is as follows:
s2: preparation of side-chain type liquid crystal polymer containing benzoxazole liquid crystal element
After the benzoxazole liquid crystal element prepared in the step S1 reacts with 1, 4-dioxane and polyepichlorohydrin, the side chain type liquid crystal polymer containing the benzoxazole liquid crystal element is obtained by settling in absolute ethyl alcohol, and the structural formula is as follows:
wherein x/y is more than or equal to 0.2/1 and less than or equal to 1.2/1.
S3: preparation of side-chain type liquid crystal ionomer containing benzoxazole liquid crystal elements
Reacting the side chain type liquid crystal polymer containing the benzoxazole liquid crystal element prepared by S2 with dimethyl sulfoxide and N-methylimidazole, and washing with anhydrous diethyl ether to obtain the side chain type liquid crystal ionomer containing the benzoxazole liquid crystal element, wherein the structural formula is as follows:
wherein x/y is more than or equal to 0.2/1 and less than or equal to 1.2/1.
The step S1 is performed by the following method as a limitation:
reacting p-hydroxybenzaldehyde, 1, 6-dibromohexane, anhydrous potassium carbonate and N, N-dimethylformamide at 70-80 ℃ for 8-10 hours, and separating and purifying by column chromatography to obtain an intermediate product A;
reacting the intermediate product A with 2-amino-4-chlorophenol and dichloromethane at 30-50 ℃ for 5-7 hours, and recrystallizing with absolute ethyl alcohol to obtain an intermediate product B;
reacting the intermediate product B with dichlorodicyanobenzoquinone for 5-7 hours at the temperature of 60-65 ℃, and recrystallizing after column chromatography separation and purification to obtain an intermediate product C;
dissolving the intermediate product C and thiourea in absolute ethyl alcohol, reacting the mixture for 3-5 hours at 70-90 ℃ under the protection of nitrogen, adding a sodium hydroxide aqueous solution, continuing to react for 3-5 hours, cooling the mixture to 45-50 ℃, adjusting to be acidic, continuing to cool to 0 ℃, performing suction filtration, washing the obtained solid with ice water, recrystallizing in absolute ethyl alcohol, filtering, and drying in vacuum at 50-55 ℃ to obtain the benzoxazole liquid crystal cell.
As a further limitation of the above definition, the p-hydroxybenzaldehyde, 1, 6-dibromohexane, anhydrous potassium carbonate, and N, N-dimethylformamide are in a molar ratio of 1:3:2: 50; the mol ratio of the intermediate product A to the 2-amino-4-chlorophenol is 1: 1.2; the molar ratio of the intermediate product B to the dichloro dicyano benzoquinone is 1: 1.2; the molar ratio of the intermediate product C to the thiourea was 1: 1.2.
As another limitation, the step S2 is performed by the following method:
under the protection of inert gas, dissolving the benzoxazole liquid crystal primitive prepared in the step S1 in 1, 4-dioxane, adding NaH, reacting for 15-20 minutes, adding polyepichlorohydrin and tetrabutylammonium bromide, reacting for 3-8 hours at 100 ℃, after the reaction is finished, settling the supernatant in absolute ethyl alcohol, uniformly mixing at 80-85 ℃, repeatedly heating and washing until the liquid crystal monomer is completely removed, and drying the obtained product at 50-55 ℃ in vacuum to obtain the side chain type liquid crystal polymer containing the benzoxazole liquid crystal primitive.
As a further limitation of the above definition, the molar ratio of the benzoxazole mesogen, 1, 4-dioxane, and polyepichlorohydrin is 1:20-30: 0.7-1.5; the number average molecular weight of the polyepichlorohydrin is 70000.
As still another limitation, the step S3 is performed by:
dissolving the side chain type liquid crystal polymer containing the benzoxazole liquid crystal elements prepared in the step S2 in dimethyl sulfoxide at 75-80 ℃, cooling to 55-60 ℃, dropwise adding N-methylimidazole into the solution, reacting for 70-80 hours, repeatedly washing with anhydrous ether after the reaction is finished until unreacted raw materials are removed, and drying the obtained product at 45-50 ℃ in vacuum to obtain the side chain type liquid crystal ionomer containing the benzoxazole liquid crystal elements.
As a further limitation of the above limitation, the side chain type liquid crystal polymer containing the benzoxazole liquid crystal moiety, the dimethyl sulfoxide and the N-methylimidazole have a molar ratio of 1:20: 1.4-2.
Due to the adoption of the technical scheme, compared with the prior art, the invention has the technical progress that:
(1) the side chain type liquid crystal ionomer containing benzoxazole liquid crystal elements has the advantages that the liquid crystal elements of the side chain type liquid crystal ionomer connect the liquid crystal monomers with the main chain through nucleophilic substitution reaction, the defect that the traditional ester bond connection is easy to hydrolyze is avoided, the stability is good under certain humidity and acid/alkali environment, the side chain type liquid crystal ionomer is not easy to hydrolyze, and the side chain type liquid crystal ionomer has good liquid crystal performance;
(2) the side chain type liquid crystal ionomer containing benzoxazole liquid crystal elements has obvious smectic phase focal conic texture in the processes of heating and cooling, and can improve the ion conduction capability and construct an ordered ion channel. And thus is suitable for developing a polymer electrolyte fuel cell for a liquid crystal ionomer membrane electrode;
(3) the preparation method of the side chain type liquid crystal ionomer containing benzoxazole liquid crystal elements has the advantages of simple preparation process, reasonable limitation on the molecular weight of raw materials, reasonable raw material proportion, strict control of reaction time and good output effect;
in conclusion, the invention is applicable to the technical field of materials, and has wide value in the field of liquid crystal materials and the field of fuel cell development, such as improvement of ion conductivity and construction of ordered ion channels.
Drawings
The invention will be described in more detail with reference to the following figures and embodiments:
the accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention;
FIG. 1 is a nuclear magnetic resonance hydrogen spectrum of a benzoxazole mesogen side chain type liquid crystal ionomer obtained in example 1;
FIG. 2 is a DSC curve chart of the benzoxazole mesogen side chain type liquid crystal ionomer prepared in example 1 measured at a temperature rise and fall rate of 5 ℃/min; the downward curve in the figure represents the DSC curve of the ionomer during temperature increase, with a distinct phase transition temperature; the upward curve in the figure represents the DSC curve of the ionomer during temperature decrease, with a distinct phase transition temperature;
FIG. 3 is a POM photograph at a temperature of 141.80 ℃ at 50 times magnification of a benzoxazole mesogen side chain type liquid crystal ionomer obtained in example 1; showing a significant smectic phase focal conic texture;
FIG. 4 is a POM photograph at a reduced temperature of 138.90 ℃ and at a magnification of 50 times of a benzoxazole mesogen side chain type liquid crystal ionomer prepared in example 1; showing a significant smectic phase focal conic texture;
FIG. 5 is a graph showing the temperature dependence of the electrical conductivity of the side-chain type liquid crystal ionomer of benzoxazole mesogen prepared in example 1; the conductivity increases with increasing temperature.
Detailed Description
Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the description of the preferred embodiment is only for purposes of illustration and understanding, and is not intended to limit the invention.
Example 1A side-chain type liquid crystal ionomer containing benzoxazole mesogen and a method for preparing the same
A side chain type liquid crystal ionomer containing benzoxazole liquid crystal elements has a structural formula as follows:
wherein x/y is 0.2/1.
The preparation method of the side chain type liquid crystal ionomer containing benzoxazole liquid crystal elements comprises the following steps:
s1: preparation of benzoxazole mesogen
Adding 4.88g (39.90mmol) of p-hydroxybenzaldehyde, 29.20g (119.70mmol) of 1, 6-dibromohexane, 11.01g (79.80mmol) of anhydrous potassium carbonate and 145.81g (100mL) of N, N-dimethylformamide into a 250mL single-neck flask provided with a magnetic stirrer and a spherical condenser tube, stirring at 80 ℃ for 8 hours, and separating and purifying by column chromatography to obtain an intermediate product A;
stirring intermediate product A4.98g (17.46mmol), 2-amino-4-chlorophenol 3.01g (20.95mmol) and 40mL of dichloromethane at 45 ℃ for 6 hours, and recrystallizing with absolute ethanol to obtain intermediate product B;
5.99 g (14.60mmol) of the intermediate product B and 3.89g (17.52mmol) of dichlorodicyanobenzoquinone continue to react for 6 hours at 61 ℃, and after separation and purification by column chromatography, the intermediate product C is obtained by recrystallization;
dissolving intermediate product C3.50g (8.55mmol) and thiourea 0.78g (10.26mmol) in 60mL of absolute ethanol, reacting the mixture at 80 ℃ for 4 hours under the protection of nitrogen, adding NaOH aqueous solution (1g/15mL), continuing to react for 4 hours, cooling the mixture to 50 ℃, adding dilute sulfuric acid to adjust the mixture to be acidic (pH is 2), continuing to cool to 0 ℃, performing suction filtration by using a Buchner funnel, washing the obtained solid with ice water three times, performing pure crystallization in absolute ethanol, filtering, and drying in a vacuum oven at 55 ℃ for 24 hours to obtain the benzoxazole liquid crystal unit with the following structural formula:
the spectral analysis data of the benzimidazole mesogen are as follows:
1H-NMR(400MHz,CDCl3,TMS):
8.17-8.10(dd,3JH-H＝8.98Hz,4JH-H＝2.37Hz,2H),7.69-7.66(d,4JH-H＝1.27Hz,1H),7.47-7.43(d,3JH-H＝8.67Hz,1H),7.29-7.25(m,1H),7.02-6.96(dd,3JH-H＝8.94Hz,4JH-H＝2.33Hz,2H),4.10-3.94(t,3JH-H＝6.33Hz,3H),2.73-2.66(t,3JH-H＝7.26Hz,3H),2.56-2.49(t,3JH-H＝7.45Hz,3H),1.87-1.76(m,2H),1.67-1.56(m,2H),1.56-1.41(m,4H).
IR(KBr)v(cm-1):3445,2937,2855,1607,1502,1445,1249,1168,1047,1018,914,833,792,735.
EI-MS m/z(rel.int.):362.92(M+,25),244.90(62),206.92(100),190.92(115),132.94(14)。
through1H-NMR, IR and EI-MS data confirmed that the structure of the product obtained was consistent with that of the target compound.
S2: preparation of side-chain type liquid crystal polymer containing benzoxazole liquid crystal element
Under the protection of nitrogen, 2.48g (6.85mmol) of the benzoxazole liquid crystal compound prepared in step S1 was dissolved in 20mL (171.25mmol) of 1, 4-dioxane, 0.16g (6.67mmol) of NaH was added thereto, and after 20 minutes of reaction, 0.95g (10.28mmol) of polyepichlorohydrin and 0.22g (0.68mmol) of TBAB were added, and the reaction was continued at 100 ℃ for 3 hours. After the reaction is finished, settling the supernatant in absolute ethyl alcohol, stirring and uniformly mixing at 80 ℃ to dissolve unreacted liquid crystal monomers, repeatedly heating and washing for many times until the liquid crystal monomers are completely removed, putting the obtained product into a vacuum oven, and drying at 55 ℃ for 24 hours to obtain the side chain type liquid crystal polymer containing benzoxazole liquid crystal elements, wherein the structural formula is as follows:
wherein x/y is 0.2/1
S3: preparation of side-chain type liquid crystal ionomer containing benzoxazole liquid crystal elements
Dissolving 1.24g (4.41mmol) of the side chain type liquid crystal polymer containing the benzoxazole liquid crystal primitives prepared in the step S2 in 20mL (88.21mmol) of dimethyl sulfoxide at 80 ℃ to form a homogeneous solution, cooling the reaction solution to 60 ℃, dropwise adding 0.97g (6.17mmol) of excessive N-methylimidazole into the solution, continuing to react for 72 hours, repeatedly washing reactants with anhydrous ether after the reaction is finished until unreacted raw materials are removed, and drying the product in a vacuum oven at 45 ℃ for 48 hours to obtain the side chain type liquid crystal ionomer containing the benzoxazole liquid crystal primitives, wherein the structural formula is as follows:
wherein x/y is 0.2/1.
Examples 2 to 6A method for preparing a side-chain type liquid crystalline ionomer containing benzoxazole-containing mesogen
Examples 2 to 3 are methods for preparing side-chain type liquid crystal ionomers containing benzoxazole mesogens, respectively, the method for preparing the related liquid crystal ionomer is similar to that of example 1, except that fine adjustment and process parameters of the general knowledge in the art are combined in the preparation process, and the process parameters are shown in table 1:
table 1 examples 2-6 process parameters
Wherein x/y in the side chain type liquid crystal ionomer containing benzimidazole mesogen prepared in example 2 is 0.2/1; x/y in the side-chain type liquid crystal ionomer containing benzimidazole mesogen prepared in example 3 is 0.3/1; x/y in the side chain type liquid crystal ionomer containing benzimidazole mesogen prepared in example 4 is 0.5/1; the x/y of the side-chain type liquid crystal ionomer containing benzimidazole mesogen prepared in example 5 is 1/1; the side chain type liquid crystal ionomer containing benzimidazole mesogen prepared in example 6 had x/y of 1.2/1.
Example 7 Structure, thermal behavior and Electrical Performance testing of side-chain type liquid Crystal ionomers containing benzoxazole mesogens
The structure, thermal behavior and electrical properties of the side chain type liquid crystal ionomer containing benzoxazole liquid crystal elements prepared in example 1 are measured, wherein the phase transition temperature and the phase transition enthalpy are measured by a differential scanning calorimeter; the ionic conductivity was measured by an impedance meter and the results were as follows:
FIG. 1 is a nuclear magnetic resonance hydrogen spectrum of a side chain type liquid crystal ionomer containing benzoxazole mesogen of example 1. As can be seen from FIG. 1, the structure of the side chain type liquid crystal ionomer containing benzoxazole mesogen of the present invention is in accordance with the expected assumption.
TABLE 1 phase transition temperature and enthalpy of phase transition
Note: in table 6SHPBC represents a liquid crystal monomer; PLC stands for liquid crystal polymer; LCI represents a liquid crystal ionomer; sm represents a smectic phase; cr represents a crystalline phase; i represents isotropy.
TABLE 2 chloride conductivity and ion exchange Capacity
Note: in the table, σ represents the conductivity
As can be seen from Table 1, the side chain type liquid crystal ionomer containing benzoxazole mesogen of the present invention has thermotropic tautomeric liquid crystal properties. The liquid crystal phase zones of temperature rise and temperature drop are respectively 5.64 ℃ and 31.15 ℃.
As is clear from Table 2, the side-chain type liquid crystal ionomer comprising benzoxazole-containing mesogen of the present invention has an Ion Exchange Capacity (IEC) of 0.12mequiv/g and a chloride ion conductivity of 20.68mS/cm at 80 ℃. The liquid crystal ionomer structure is shown to have chloride ion conductivity and ion exchange capacity, and contains ionized groups.
FIG. 2 is a DSC curve of the benzoxazole mesogen side chain type liquid crystal ionomer of example 1 measured at a temperature rise and fall rate of 5 ℃/min. FIG. 3 is a POM photograph of the benzoxazole mesogen side chain type liquid crystal ionomer of example 1 at a temperature of 141.80 ℃ with 50 times magnification. FIG. 4 is a POM photograph of the benzoxazole mesogen side chain type liquid crystal ionomer of example 1 at reduced temperature 138.90 ℃ with 50 times magnification. As can be seen from the DSC curve of fig. 2 and POM photographs of fig. 3 and 4, the compound of the present invention has a liquid crystal texture of smectic phase and a liquid crystal phase at both increasing and decreasing temperatures.
FIG. 5 is a graph showing the temperature-dependent change of conductivity of the side-chain type liquid crystal ionomer containing benzoxazole mesogen of example 1. As can be seen from FIG. 5, the chloride ion conductivity of the side-chain type liquid crystal ionomer containing benzoxazole mesogen of the present invention increases with the increase of temperature.
The structure, thermal behavior and electrical properties of the side chain type liquid crystal ionomer containing benzoxazole lc molecules prepared in examples 2-6 were tested, and the liquid crystal ionomer also has an obvious smectic phase focal conic texture and a wide liquid crystal phase interval, but the conductivity is reduced due to the improvement of the substitution degree of the liquid crystal monomer for the following reasons:
the side chain type liquid crystal ionomer liquid crystal element of the invention connects the liquid crystal monomer with the main chain through nucleophilic substitution reaction, and because of the characteristic of stable C-S bond structure, the defect of easy hydrolysis of traditional ester bond connection is avoided, therefore, the side chain type liquid crystal ionomer liquid crystal element has good stability under certain humidity and acid/alkali environment, is not easy to hydrolyze, and simultaneously has obvious smectic phase focal conic texture, wide liquid crystal phase interval and other liquid crystal performances.
Example 8 application of side-chain type liquid Crystal ionomer containing benzoxazole liquid Crystal moiety
A liquid crystal ionomer film is prepared by using the side chain type liquid crystal ionomer containing benzoxazole liquid crystal elements prepared in example 1, and the specific method is as follows:
and (3) completely dissolving the polyepichlorohydrin liquid crystal ionomer into a trichloromethane solution, pouring the solution into a watch glass, forming a film after the solvent is volatilized, and standing for later use.
The liquid crystal ionomer film was cut into five rectangular sheets of 5mm × 15mm size and tested in an impedance meter (Hioki3532-80), and as a result, the chloride ion conductivity was 20.68mS/cm as shown in table 2, and the side chain type liquid crystal ionomer film containing benzoxazole mesogen prepared in this example exhibited thermotropic liquid crystal characteristics.
The application of the side chain type liquid crystal ionomer containing benzoxazole provided in this example to prepare liquid crystal ionomer films is also applicable to examples 2-6.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A side chain type liquid crystal ionomer containing benzoxazole liquid crystal elements is characterized in that the structural formula of the polymer is as follows:
wherein x/y is more than or equal to 0.2/1 and less than or equal to 1.2/1.
2. The method for preparing the side chain type liquid crystal ionomer containing benzoxazole mesogen as claimed in claim 1, comprising the steps of:
s1: preparation of benzoxazole mesogen
Reacting p-hydroxybenzaldehyde, 1, 6-dibromohexane, anhydrous potassium carbonate and N, N-dimethylformamide, and separating and purifying to obtain an intermediate product A;
reacting the intermediate product A, 2-amino-4-chlorophenol and dichloromethane, and recrystallizing to obtain an intermediate product B;
reacting the intermediate product B with dichlorodicyano benzoquinone, separating, purifying and recrystallizing to obtain an intermediate product C;
reacting the intermediate product C and thiourea with absolute ethyl alcohol and sodium hydroxide to obtain benzoxazole liquid crystal cells, wherein the structural formula is as follows:
s2: preparation of side-chain type liquid crystal polymer containing benzoxazole liquid crystal element
After the benzoxazole liquid crystal element prepared by S1 reacts with 1, 4-dioxane and polyepichlorohydrin, the side chain type liquid crystal polymer containing the benzoxazole liquid crystal element is obtained by settling in absolute ethyl alcohol, and the structural formula is as follows:
wherein x/y is more than or equal to 0.2/1 and less than or equal to 1.2/1;
s3: preparation of side-chain type liquid crystal ionomer containing benzoxazole liquid crystal elements
Reacting the side chain type liquid crystal polymer containing the benzoxazole liquid crystal element prepared by S2 with dimethyl sulfoxide and N-methylimidazole, and washing with anhydrous diethyl ether to obtain the side chain type liquid crystal ionomer containing the benzoxazole liquid crystal element, wherein the structural formula is as follows:
wherein x/y is more than or equal to 0.2/1 and less than or equal to 1.2/1.
3. The method for preparing side-chain type liquid crystal ionomer containing benzoxazole mesogen according to claim 2, wherein the step S1 is performed by the following steps:
reacting p-hydroxybenzaldehyde, 1, 6-dibromohexane, anhydrous potassium carbonate and N, N-dimethylformamide at 70-80 ℃ for 8-10 hours, and separating and purifying by column chromatography to obtain an intermediate product A;
reacting the intermediate product A with 2-amino-4-chlorophenol and dichloromethane at 30-50 ℃ for 5-7 hours, and recrystallizing with absolute ethyl alcohol to obtain an intermediate product B;
reacting the intermediate product B with dichlorodicyanobenzoquinone for 5-7 hours at the temperature of 60-65 ℃, and recrystallizing after column chromatography separation and purification to obtain an intermediate product C;
dissolving the intermediate product C and thiourea in absolute ethyl alcohol, reacting the mixture for 3-5 hours at 70-90 ℃ under the protection of inert gas, adding a sodium hydroxide aqueous solution, continuing to react for 3-5 hours, cooling the mixture to 45-50 ℃, adjusting to be acidic, continuing to cool to 0 ℃, performing suction filtration, washing the obtained solid with ice water, recrystallizing in absolute ethyl alcohol, filtering, and drying in vacuum at 50-55 ℃ to obtain the benzoxazole liquid crystal cell.
4. The method for preparing side-chain type liquid crystal ionomer containing benzoxazole mesogen according to claim 2 or 3, wherein the step S1 is performed
The molar ratio of the p-hydroxybenzaldehyde to the 1, 6-dibromohexane to the anhydrous potassium carbonate to the N, N-dimethylformamide is 1:3:2: 50;
the mol ratio of the intermediate product A to the 2-amino-4-chlorophenol is 1: 1.2;
the molar ratio of the intermediate product B to the dichloro dicyano benzoquinone is 1: 1.2;
the molar ratio of the intermediate product C to the thiourea was 1: 1.2.
5. The method for preparing side-chain type liquid crystal ionomer containing benzoxazole mesogen according to claim 2, wherein the step S2 is performed by the following steps:
under the protection of inert gas, dissolving the benzoxazole liquid crystal primitive prepared in the step S1 in 1, 4-dioxane, adding NaH, reacting for 15-20 minutes, adding polyepichlorohydrin and tetrabutylammonium bromide, reacting for 3-8 hours at 100 ℃, after the reaction is finished, settling the supernatant in absolute ethyl alcohol, uniformly mixing at 80-85 ℃, repeatedly heating and washing until the liquid crystal monomer is completely removed, and drying the obtained product at 50-55 ℃ in vacuum to obtain the side chain type liquid crystal polymer containing the benzoxazole liquid crystal primitive.
6. The method for preparing side-chain type liquid crystal ionomer containing benzoxazole mesogen according to claim 2 or 5, wherein the step S2 is performed
The molar ratio of the benzoxazole liquid crystal element to the 1, 4-dioxane to the polyepichlorohydrin is 1:20-30: 0.7-1.5; the number average molecular weight of the polyepichlorohydrin is 70000.
7. The method for preparing side-chain type liquid crystal ionomer containing benzoxazole mesogen according to claim 2, wherein the step S3 is performed by the following steps:
dissolving the side chain type liquid crystal polymer containing the benzoxazole liquid crystal elements prepared in the step S2 in dimethyl sulfoxide at 75-80 ℃, cooling to 55-60 ℃, dropwise adding N-methylimidazole into the solution, reacting for 70-80 hours, repeatedly washing with anhydrous ether after the reaction is finished until unreacted raw materials are removed, and drying the obtained product at 45-50 ℃ in vacuum to obtain the side chain type liquid crystal ionomer containing the benzoxazole liquid crystal elements.
8. The method for preparing the side-chain type liquid crystal ionomer containing benzoxazole mesogen as claimed in claim 2 or 7, wherein the step S3 is performed
The side chain type liquid crystal polymer containing benzoxazole liquid crystal elements, dimethyl sulfoxide and N-methylimidazole have the molar ratio of 1:20: 1.4-2.
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